We present a study of the density structure of the protostellar collapse candidate B335 using continuum observations from the IRAM Plateau de Bure Interferometer made at wavelengths of 1.2 mm and 3.0 mm .
We analyze these data , which probe spatial scales from 5000 AU to 500 AU , directly in the visibility domain by comparison to synthetic observations constructed from models that assume different physical conditions .
This approach allows for much more stringent constraints to be derived from the data than from analysis of images .
A single radial power law in density provides a good description of the data , with best fit power law density index p = 1.65 \pm 0.05 .
Through simulations , we quantify the sensitivity of this result to various model uncertainties , including assumptions of temperature distribution , outer boundary , dust opacity spectral index , and an unresolved central component .
The largest uncertainty comes from the unknown presence of a centralized point source .
The maximal point source with 1.2 mm flux of F = 12 \pm 7 mJy reduces the power law density index to p = 1.47 \pm 0.07 .
The remaining sources of systematic uncertainty , of which the most important is the radial dependence of the temperature distribution , likely contribute a total uncertainty at the level of \delta p \lesssim 0.2 .
Taking account the uncertainties , we find strong evidence that the power law index of the density distribution within 5000 AU is significantly less than the value at larger radii , close to 2.0 from previous studies of dust emission and extinction .
Images made from the data show clear departures from spherical symmetry , with the globule being slightly extended perpendicular to the outflow axis .
The inclusion of a crude model of the outflow as a hollowed bipolar cone of constant opening angle improves the fit and leaves the resulting density power law index unchanged .
These results conform well to the generic paradigm of isolated , low-mass star formation which predicts a power law density index close to p = 1.5 for an inner region of gravitational free fall onto the protostar .
However , the standard inside-out collapse model does not fit the data as successfully as a simple p = 1.5 power law because of the relative shallowness of the predicted density profile just within the infall radius .